title: Abnormal small airways function in children with mild asthma.
abstract: BACKGROUND
  Small airways disease is a hallmark in adults with persistent asthma, but little is known about small airways function in children with mild asthma and normal spirometry. We assessed ventilation heterogeneity, a marker of small airways function, with an easy tidal breath single-breath washout (SBW) technique in school-aged children with mild asthma and normal FEV1 and healthy age-matched control subjects.
  
  
  METHODS
  The primary outcome was the double-tracer gas phase III slope (SDTG), an index of ventilation heterogeneity in acinar airways derived from the tidal double-tracer gas SBW test. The second outcome was the nitrogen phase III slope (SN2), an index of global ventilation heterogeneity derived from the tidal nitrogen SBW test using pure oxygen. Triplicate SBW and spirometry tests were performed in healthy children (n=35) and children with asthma (n=31) at baseline and in children with asthma after bronchodilation.
  
  
  RESULTS
  Acinar (SDTG) but not global (SN2) ventilation heterogeneity was significantly increased in asthma despite normal FEV1. Of the 31 children with asthma, abnormal results were found for SDTG (≤-2 z scores) in 11; forced expiratory flow, midexpiratory phase (FEF25%-75%) in three; and FEV1 in zero. After bronchodilation, SDTG, SN2, FEF25%-75%, and FEV1 significantly changed (mean [95% CI] change from baseline, 36% [15%-56%], 38% [18%-58%], 17% [9-25%], and 6% [3%-9%], respectively).
  
  
  CONCLUSIONS
  Abnormal acinar ventilation heterogeneity in one-third of the children suggests that small airways disease may be present despite rare and mild asthma symptoms and normal spirometry. The easy tidal SBW technique has considerable potential as a clinical and research outcome in children with asthma.
authors.affiliation: University Children's Hospital Zurich, Zurich; University Children's Hospital Bern, Bern.
authors.forename: Florian
authors.initials: F
authors.lastname: Singer
authors.affiliation: University Children's Hospital Bern, Bern.
authors.forename: Chiara
authors.initials: C
authors.lastname: Abbas
authors.affiliation: University Children's Hospital Bern, Bern; University Children's Hospital Basel, Basel, Switzerland.
authors.forename: Sophie
authors.initials: S
authors.lastname: Yammine
authors.affiliation: University Children's Hospital Bern, Bern.
authors.forename: Carmen
authors.initials: C
authors.lastname: Casaulta
authors.affiliation: University Children's Hospital Zurich, Zurich; University Children's Hospital Basel, Basel, Switzerland.
authors.forename: Urs
authors.initials: U
authors.lastname: Frey
authors.affiliation: University Children's Hospital Bern, Bern; University Children's Hospital Basel, Basel, Switzerland. Electronic address: philipp.latzin@ukbb.ch.
authors.forename: Philipp
authors.initials: P
authors.lastname: Latzin
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000175:diagnosis / Q000503:physiopathology*; D016084:Bronchoconstriction / Q000502:physiology*; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume / Q000502:physiology*; D006801:Humans; D008297:Male; D011446:Prospective Studies; D013147:Spirometry